SUPERGEN Wind Wind Energy Technology Phase 2

Theme 2 – The Turbine Dr Geoff Dutton

Supergen Wind Phase 2 – General Assembly Meeting

21 March 2012

Rotor wind-field

interaction

Turbine blade

materials Drive train

dynamics

Fault detection

0 100 200 300 400 500 600 700 800-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency [Hz]

No

rma

lize

d s

pe

ctru

m [d

B]

MODEL

RIG

112 Hz

212 Hz

150 Hz

373.8 Hz

435.7 Hz

273.8 Hz

535.7 Hz

597.6 Hz

697.6 Hz

250 Hz 350 Hz

Subsea turbine foundations

The

Turbine

Middelgrunden wind farm – photo by LM

Glasfiber

The

Turbine

• Basic materials

• 3D fabrics and joints

• Component testing

• Blade model

Turbine blade

materials

Reliable and cost-effective

wind turbine blades

Selection of

materials and

manufacturing

process design

Weight Bending

stiffness

Cost

Fatigue

Resistance Manufacturing

processes

Labour,

Material,

Equipment

Production rate

Maintenance

and repair

Environmental effects:

UV, radar,

Corrosions,

Lightening

Materials considerations in blade design

• Selective interfacial reinforcement

• Veils

• Nano-additives

• Through-thickness stitching and tufting

• Use of 3D fibre formats: braiding & weaving

3D Fabric

Novel materials: interlaminar toughness

Nano silica particles

• Why 3D Textiles?

Current UD prepreg technology is excellent for thin flat structures

But……

• It is slow to lay up, difficult to work with complex 3D shapes, and struggles to allow load transfer in connections and across right angle shapes.

3D textile composites

Slide

No.7

1

2

0.006

0.007

0.008

0.009

0.010

0.011

0.012

0.013

0.014

2.0 2.5 3.0 3.5 4.0 4.5 5.0

Log (N)S

tra

in

Mean strain on

stitched line

Mean strain

between two

stitched lines

Mean strain of

stitched sample

Mean strain of

unstitched

sample

1

2

(a) (b) (c) (d)

Fig. Principal strain for samples. Arrows indicate the

stitching lines.

Fig. history of strain variations over stitched (line 1) and

unstitched (line 2) areas

Unstitched

400 cycles

Unstitched

17,000 cycles

Stitched

400 cycles

Stitched

17,000 cycles

• Stitching generates high strain concentration areas along the sample.

• The strains on stitching line are much higher than unstitched area.

• The strains on stitching line are increasing gradually while the fatigue test is ongoing.

However, the average strains of the stitched sample exhibit almost same values as that

of the unstitched sample during the fatigue test.

Stitching: Digital Image Correlation

Structural blade model Materials

Parametric blade model: – 3D coupled shell/solid

element model

– Geometry sweeps

– Realistic quasi-static aerodynamic/gravity load

– Static failure criteria

– Cohesive failure model for shear web bonding line

– “First look” fatigue strength analysis

– Lay-up optimisation (under development)

Structural blade model Fully distributed aerodynamic loading

The

Turbine

• Vortex lattice wake model

• Transient rotor load model

• Integrated wake/rotor model

• Wind tunnel model testing

Rotor wind-field

interaction

Rotor Wind Field Interaction: Unsteady Vortex Lattice Wake Model

 

G1

GM

é

ë

ê ê ê

ù

û

ú ú ú

=

C11 C1N

CM 1 CMN

é

ë

ê ê ê

ù

û

ú ú ú

-1V1

VN

é

ë

ê ê ê

ù

û

ú ú ú

Rotor Wind Field Interaction: Wind Tunnel Model Testing

Rotor Wind Field Interaction: Transient Rotor Load Model

Rotor Wind Field Interaction: Transient Rotor Load Model

Rotor Wind Field Interaction:

Use model to simulate the flow conditions surrounding a turbine in an array

Study the effects of upstream rotor wake interaction on downstream turbines.

Investigate the effects of wind shear and incident turbulence on the rotor loads.

Develop semi-empirical models for use with industry standard BEM codes to predict the impact on rotor induction factors and loading of these unsteady flow conditions.

The

Turbine

• Improving controllers

• Flexibility of operation

• Control of model blade devices

Drive train

dynamics

Improving controllers Bode Plot before Gain Scheduling

tower blade

edge

increasing

size

Non-linearities due

to blade pitching

Improving controllers Bode Plot after Gain Scheduling

Flexibility of operation

Flexibility of operation General layout of the controller

“Outer” controller (independent of the wind turbine’s inner controller)

Applicable to any wind turbine, regardless of the specific design of the inner controller and without any effect under normal conditions General layout of the

additional power controller

The

Turbine

• Application of monitoring techniques

• Monitoring key sub-assemblies

Fault detection

0 100 200 300 400 500 600 700 800-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency [Hz]

No

rma

lize

d s

pe

ctru

m [d

B]

MODEL

RIG

112 Hz

212 Hz

150 Hz

373.8 Hz

435.7 Hz

273.8 Hz

535.7 Hz

597.6 Hz

697.6 Hz

250 Hz 350 Hz

Why is fault detection needed?

• Generator and gearbox failures contribute significantly to wind turbine downtime

• Generators and gearboxes have v. high replacement costs

• Spectral analysis of vibration signals commonly used in commercial condition monitoring systems for fault detection

• Spectral analysis of line current common in other fields for detection of motor/generator faults

Aims of fault detection

• Fundamental understanding of potential failure mechanisms and resulting fault signals in generators, drive train and frequency converters

• Develop practical methods of tracking fault signals under normal operating conditions

• Extend to all generator types and associated supply converters

• Mixed signal sources: current, power, vibration, temperature etc

Drive Train Test Rigs

DFIG generator and frequency converter rig at Manchester:

- Fixed speed Synchronous wound-rotor generator and gearbox rig at Durham: - Variable speed - SKF WindCon

Screened test chamber for PD testing at Manchester

Generator Fault

• Wound rotor induction generator rotor electrical asymmetry

– eg slip-ring/brush gear fault/unbalance

Raw data of generator speed, current and instantaneous power

Example of fault frequency tracking the power under wind conditions – 2sf component tracked : onset of rotor asymmetries clearly evident

0 100 200 300 400 500 600 700 800-60

-50

-40

-30

-20

-10

0

Frequency [Hz]

No

rma

lize

d s

pe

ctru

m [d

B]

MODEL

RIG

273.8 Hz

373.8 Hz597.6 Hz

697.6 Hz150 Hz

250 Hz 350 Hz

450 Hz

0 100 200 300 400 500 600 700 800-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency [Hz]

No

rma

lize

d s

pe

ctru

m [d

B]

MODEL

RIG

112 Hz

212 Hz

150 Hz

373.8 Hz

435.7 Hz

273.8 Hz

535.7 Hz

597.6 Hz

697.6 Hz

250 Hz 350 Hz

a) Healthy DFIG b) Stator winding fault

• DFIG induction generator stator winding fault

• Line current frequency spectra – all frequency components can be identified in healthy and faulted operation using detailed generator model

Generator Fault

0 50 100 15010

-5

10-4

10-3

10-2

10-1

100

Stator current frequency spectrum, 1600 rpm

Frequency [Hz]

I s [nor

maliz

ed]

healthy

faulthy

fo-fs

2fo-f

sfo+f

s

Conventional stator current spectrum – difficult to see bearing fault signal!

80 90 100 110 120 130 140 150 160 170

10-4

10-3

10-2

10-1

100

Frequency [Hz]

Acce

lera

tio

n [

m/s

2]

Vibration frequency spectrum 1600 rpm

healthy

faulthy

2fo

fo

Vibration signal – bearing fault signal clear

81 82 83 84 85 860

2

4

6

8

10

12

14

16

x 10-3 Complex envelope frequency spectrum, 1630 rpm

Frequency [Hz]

ma

gn

itu

de

[n

orm

aliz

ed

]

Ias

Ibs

Ics

fo

Modified current spectrum –

bearing fault signal now clear!

• Stator current – see electrical

faults and bearing faults!

• Vibration signal – see bearing

fault and electrical faults!

Induction generator - outer race bearing fault

Ongoing work

• Bearing faults in DFIG’s • Detection of converter faults • Develop link from condition

monitoring to maintenance • Electrical fault models for

other generator types (eg direct-drive/hybrid pm generators)

• PD test facility: signal comparison for two methods: blue signal from a discharge detector Robinson M5, yellow from a 25-2000 MHz scan antenna

Subsea turbine foundations

The

Turbine • Extend hydrodynamic

solver to waves

• Historical data and experiment design

• Experimental study of wave loading

• Solver optimisation

• Numerical experiments

Experiments and Theoretical analyses conducted by D.L. Kriebel (1998) and J.R. Chaplin et al. (1997)

NWT outer dimensions: 8 × 3.6 × 0.9 m3

Water depth : h = 0.45m Diameter of cylinder : d = 0.325m

Case1 Case2 Case3 Case4

Wave amplitude (m) 0.0535 0.048 0.0621 0.074

Wave period (s) 1.95 1.75 1.50 1.25

Scattering parameter ka 0.271 0.308 0.374 0.481

wave gauges

Wave impact on a vertical cylinder

-100

-50

0

50

100

0 1 2 3 4 5 6 7 8 9 10

Forc

e (N

)

t (s)

-100

-50

0

50

100

150

0 1 2 3 4 5 6 7 8 9 10

Forc

e (N

)

t (s)

-100

-50

0

50

100

0 1 2 3 4 5 6 7 8 9 10

Forc

e (N

)

t (s)

Time history of horizontal force on cylinder

-100

-50

0

50

100

0 1 2 3 4 5 6 7 8 9 10

Forc

e (N

)

t (s)

1

2

3

4

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

-3.14 -1.57 0 1.57 3.14

F/F

0

Phase

Numerical Linear theory Second order Experimetal

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

-3.14 -1.57 0 1.57 3.14

F/F

0

Phase

Numerical

Linear theory

Second order

Experimental

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

-3.14 -1.57 0 1.57 3.14

F/F

0

Phase

Numerical

Linear theory

Second order

Experimental

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

-3.14 -1.57 0 1.57 3.14

F/F

0

Phase

Numerical

Linear theory

Second order

Experimental

Wave force time series for combinations of ka and kH (d/a=2.77)

Case2:

ka = 0.308, kH = 0.182

Case1:

ka = 0.271, kH = 0.178

Case4:

ka = 0.481, kH = 0.438

Case3:

ka = 0.374, kH = 0.286

(1) t = 0/8 T (2) t = 1/8 T (3) t = 2/8 T

(4) t = 3/8 T (5) t = 4/8 T (6) t = 5/8 T

(7) t = 6/8 T (8) t = 7/8 T (9) t = 8/8 T

Typical water surface around cylinder in 2nd wave period (Case1)

Extreme wave impact on a vertical cylinder

-100 -80 -60 -40 -20

0 20 40 60 80

100

3 4 5 6 7 8

Hori

zon

tal

Forc

e (N

)

t (s)

Extreme wave test

Input wave energy spectrum Time history of horizontal force on cylinder

Acknowledgements

For further information please contact:

geoff.dutton@stfc.ac.uk

EPSRC grant nos.

EP/D034566/1 & EP/H018662/1

SUPERGEN Wind Energy Technologies Consortium